1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus including the electrophotographic photosensitive member.
2. Description of the Related Art
Currently, an electrophotographic photosensitive member for use in a process cartridge and an electrophotographic apparatus is mainly an electrophotographic photosensitive member containing an organic photoconductive substance. The electrophotographic photosensitive member generally has a support and a photosensitive layer formed on the support. Then, an intermediate layer is provided between the support and the photosensitive layer for the purpose of suppressing charge injection from the support to the photosensitive layer (charge generating layer) to suppress the occurrence of an image defect such as fogging.
As the intermediate layer, an intermediate layer formed by a resin such as polyamide is known. Such an intermediate layer, however, exhibits ion conductivity, is particularly high in electric resistance under low-temperature and low-humidity, and is easily made high in residual potential.
In addition, a recent image forming apparatus in which coherent light such as laser light is used has the problem of causing an interference fringe. For the purposes of suppressing the occurrence of the interference fringe and controlling the electric resistance of the intermediate layer, a technique in which a metal oxide particle is contained in an intermediate layer is known. In such an intermediate layer containing a metal oxide particle, while the interference fringe is suppressed, the effect of suppressing fogging is easily insufficient.
In order to solve the problems, a technique has been proposed in which a first intermediate layer containing a resin and a second intermediate layer containing a metal oxide particle and a binder resin are stacked to thereby stabilize the potential of an electrophotographic photosensitive member in repeated use. For example, Japanese Patent Application Laid-Open No. 2005-189828 discloses an electrophotographic photosensitive member including a first intermediate layer containing polyamide, and a second intermediate layer containing a binder resin and a titanium oxide particle, stacked on the first intermediate layer. Japanese Patent No. 4832182 discloses an electrophotographic photosensitive member including a first intermediate layer containing polyamide and an electron transporting substance, and a second intermediate layer containing a binder resin and a titanium oxide particle, stacked on the first intermediate layer. Such conventional electrophotographic photosensitive members in which the intermediate layers are used currently satisfy a required image quality.
In recent years, however, a demand for the quality of an electrophotographic image has been increased, and the number of cases where the same image is output in large numbers in a short period of time has been increased.
In such a case, an image defect called a pattern memory easily occurs. The pattern memory refers to a phenomenon in which, when an image 301 including vertical lines 306 in FIG. 3A is continuously output in large numbers and then a solid black image 302 in FIG. 3B is output, the solid black image output is an image 304 including vertical lines 307 (FIG. 3C) caused by a repetition hysteresis of the vertical lines 306 in FIG. 3A. The pattern memory also refers to a phenomenon in which, when the image 301 in FIG. 3A is continuously output in large numbers and then a halftone image 303 in FIG. 3D is output, the halftone image output is an image 305 including vertical lines 308 (FIG. 3E) caused by the repetition hysteresis of the vertical lines 306 in FIG. 3A, as in the case of the solid black image.
The present inventors have made studies, and as a result, have found that the electrophotographic photosensitive members described in Japanese Patent Application Laid-Open No. 2005-189828 and Japanese Patent No. 4832182, in which charges are easily retained in the intermediate layers in repeated use and the pattern memory may occur, thus have a room for improvement.
The present invention is directed to providing an electrophotographic photosensitive member with a suppressed pattern memory, and a process cartridge and an electrophotographic apparatus including the electrophotographic photosensitive member.